From: Jerry Avins on 29 Apr 2010 17:57
On 4/29/2010 3:55 PM, Tauno Voipio wrote:
> The naming of pole count for bandpass filters may be coming from
> the design procedure where a low-pass prototype is constructed
> with the number of poles (3 for a 3 resonator filter). The low-pass
> prototype is then transferred to the center frequency by resonating
> each capacitor with an inductance and each coil with a capacitor,
> ignoring the extra poles brought in.
That makes the reason for bad terminology understandable, but leaves
open the kind of misunderstanding that sometimes sinks ships.
"I view the progress of science as ... the slow erosion of the tendency
to dichotomize." --Barbara Smuts, U. Mich.
From: Steve Pope on 29 Apr 2010 18:26
Mark <makolber(a)yahoo.com> wrote:
>the usual context where "pole" is mis-used is RF bandpass LC filters
>(not lowpass) where the term pole is misused refering to "resonator"
>or "tuned circuit" or "tank circuit".
>I agree... it is wrong.
I also ran into this "alternative" definition of a pole recently,
with respect to a passive RLC filter.
It can't be coincidence; I'm betting that is the way it
was taught to people in some archaic context.